This application claims the priority benefit of Japanese Patent Application No. 2001-039888, filed on Feb. 16, 2001, and entitled xe2x80x9cSolder Ball Disposing Apparatus, Solder Ball Reflow Apparatus, and Solder Ball Bonding Apparatus.xe2x80x9d
1. Technical Field
The present invention relates to an apparatus for bonding a bonding pad formed on the slider for disposing the head of a head gimbal assembly (hereafter referred to as an HG assembly), which is a component of a hard disk drive, to a lead pad formed on the tip of a lead wire with a solder ball.
2. Description of the Related Art
FIG. 7 is a perspective view of an HG assembly suitable for electrically bonding a lead wire to a slider using solder ball bonding, and FIG. 8 is a partially enlarged view of an end of the HG assembly shown in FIG. 7.
A main structure of the HG assembly 100 is composed of a base plate 101, a load beam 102, a suspension plate 103, and a flexure 104. An opening 101a is formed on the base plate 101 and a reinforcing ring 105 is fixed to the bottom side, viewed in FIG. 7, of the circumference of the opening 101a. The opening 101a is used when the HG assembly 100 is pivotably held by the HG holding means of a magnetic disk apparatus (not shown), and the HG assembly 100 pivots around the virtual vertical line 200 passing through the center of the opening 101a as the axial center in the J-K directions shown by an arrow.
An end 102a of the load beam 102 is fixed to the protruded portion 103a of the suspension plate 103 bonded to the base plate 101, and is elastically held on the base plate 101 by the suspension effect desirably obtained by the opening 103b formed in the suspension plate 103. The load beam 102 also extends in the radial direction of the virtual vertical line 200, and a tab 102b extending in the same direction is formed on another end of the load beam 102.
The flexure 104 extends from the tip of the HG assembly 100 to a multi-collector portion 104a in a crank shape, and laser-welded to the load beam 102 at joining points 107, 108, and 109, and fixed to and held by the base plate 101 at the protruded holders 101b and 101c. Four lead wires 110-113 are disposed on the upper surface (the surface seen in the upper side in FIG. 7) of the flexure 104 through an insulating sheet so as not to contact with each other. The main portions of these lead wires 110-113 are protected by protective sheets 115, 116, and 117, and the ends of these lead wires 110-113 are disposed in a line on the multi-connector portion 104a to form a connecting surface.
As shown in FIG. 8, the vicinity of the tip of the flexure 104 is fixed to the load beam 102 at the joining point 108, and the portion of the flexure 104 beyond the joining point 108 is freed from the load beam 102. In this portion, an arch-shaped opening 119 is formed, and a slider 120 is adherent and fixed to the flexure tongue 104c formed to protrude toward the center of the arch-shaped opening 119 from the platform 104b that constitutes the endmost portion of the flexure 104 (see FIG. 5).
This flexure tongue 104c is supported at a point by a pivot 102c protruded from the load beam 102 (also shown in FIG. 5 by a broken line) at the position corresponding to the center portion of the slider 120. Thereby, the slider 120 can have a prescribed amount of tilt (also often called pitch, roll, or yaw) to all direction from the load beam 102.
As shown in FIG. 7, four lead wires 110 to 113 run toward the far end forming pairs from the vicinity of the protective sheet 117, bend substantially normal at the arch-shaped opening 119 (FIG. 8) in a floating state, and terminate on the platform 104b. Here, the paired lead wires bend so as to be substantially normal to the front surface 120a of the slider 120 over two openings 121 and 122 formed between the platform 104b and the flexure tongue 104c, and further form lead pads 110a to 113a to correspond to the pad bonding surfaces of four bonding pads 123 to 126 formed on the front surface 120a of the slider 120, respectively.
Next, a bonding method by a conventional solder-ball bonding apparatus for electrically connecting four bonding pads 123 to 126 with lead pads 110a to 113a formed corresponding thereto, respectively, will be described below.
Of the above-described HG assembly, the portions other than the slider are equivalent to the slider 120 holding means. An example of this bonding method is disclosed in Japanese Patent Application No. 2000-189,148, by the present applicant. This method is implemented by a solder-boll holder 150, a suction pad 152, and an optical unit 153 shown in FIGS. 9 or 10.
The solder-ball holder 150 shown in FIG. 9 has four solder-ball holding holes 150a to 150d formed on the upper surface 150e at prescribed distances. The hopper 151 is a box-shaped member held movably in A-B direction shown by the arrow on the upper surface 150e of the solder-ball holder 150, and has a storage 151a for storing a large number of solder balls 155. On the bottom of the storage 151a is formed a slot 151b for discharging solder balls 155. When the hopper 151 moved to the discharging position to cover the four solder-ball holding holes 150a to 150d, it feeds one ball 155 to each of the solder-ball holding holes. FIG. 9 shows the state when a ball is held by each solder-ball holding hole.
The suction pad 152 is composed of a cylindrical portion 152a that has a spatially continuous hollow portion, a conical portion 152b that has a suction hole 152e at the end, a discharging pipe 152c, and a connecting portion 152 that connects these components as shown in FIG. 9. The discharging pipe 152c is connected to a suction means (not shown), and balls are discharged from the discharging pipe 152c in the timing described later.
The suction pad 152 is carried by a carrier (not shown), approaches sequentially to the four solder-ball holding holes 150a to 150d of the solder-ball holder 150, and sucks and carries the solder ball 155 held by each solder-ball holding hole. FIG. 9 shows the state when the suction pad 152 sucks and carries the solder balls.
The solder balls are carried along a prescribed route, and suction is released at the position, for example, where a solder ball 155 comes in contact with the pad bonding surface 123a of the bonding pad 123 and the bonding surface 110b of the lead pad 110a, in the HG assembly 100 held in a state tilted by about 45 degrees against the F-G direction (vertical direction). At this time, the solder ball 155 stops in the state of point contact to both bonding surfaces.
FIG. 10 is a constitutional diagram showing the state when the optical unit 153 for reflowing solder balls 155 is approached to a solder ball, which stops in contact with the pad bonding surface 123a of the bonding pad 123 and the bonding surface 110b of the lead pad 110a, as described above, together with the major constitution of the optical unit 153 itself.
The optical unit 153 is composed of a lens holder 153b that has a hollow laser-beam path space 153a formed inside and holds a series of condenser lenses 154 disposed on the laser-beam path, a nitrogen gas inlet 153c for introducing nitrogen gas N2 into the laser-beam path space 153a, a tip 153d to approach a solder ball 155 and output converged laser beams, and a laser-beam introducing port 153e connected to optical fibers 156 for introducing laser beams into the laser-beam path space 153a. 
The nitrogen gas inlet 153c has a nitrogen gas inlet 153f, and a laser-beam output opening 153g for radiating converged laser beams to the solder ball 155 is formed on the tip 153d. The optical fibers 156 are optically connected to a laser oscillator (not shown), and leads the laser beams outputted from the laser oscillator to the laser-beam introducing port 153e. 
The optical unit 153 composed as described above is moved by a moving means (not shown) to the radiating position where a part of a solder ball 155 has approached to the laser-beam output opening 153g of the optical unit 153 so as to able to enter the opening 153g. Then, nitrogen gas N2 is introduced and converged laser beams are radiated onto the solder ball 155 in the state where nitrogen gas N2 is blown to the solder ball 155 at the predetermined gas pressure, to execute solder reflow. The nitrogen gas N2 which flows out at this time, pushes the molten solder against each bonding surface, and coats the solder to prevent the solder from oxidation.
3. Problems to be Solved by the Invention
Using the above-described conventional solder-ball bonding method, if each solder ball is improperly held in each solder-ball holding hole of the solder-ball holder 150, the solder ball may be cut or broken when the hopper 151 moves. Also, since the process step to feed a solder ball into each solder-ball holding hole is independent from the process step to withdraw the solder ball from the solder-ball holding hole, the transportation work of solder balls is inefficient.
Also, since the suction pad transports solder balls one after another, the transportation of solder balls is time consuming, because aggregated traveling distance increased when a plurality of solder balls are transported, and all the transportation must be performed in high accuracy.
Also, when the reflow of solder balls is performed by radiating laser beams, since the operation is conducted in the state where nitrogen gas N2 is blown to the solder balls under a prescribed gas pressure, a hollow nitrogen-gas inlet 153c is required, thereby making the configuration of the optical unit complicated, and when the nitrogen-gas inlet 153c is installed, it is difficult to align the center of the beam path with the axis of laser beams, requiring a long time for adjustment. Furthermore, since the end portion 153d approaches a solder ball extremely closely, solder adheres the end portion easily at the time of reflow, and the maintenance of the optical unit, such as the replacement of parts, is difficult.
Furthermore, since laser beams are reflected from the inner wall of the nitrogen-gas inlet 153c or the end portion 153d, the radiation efficiency lowers, and a high-output laser is required for obtaining radiation energy required for the reflow of solder balls.
An object of the present invention is to solve these problems, and to provide a method for solder-ball bonding that excels in efficiency and workability.
A solder ball disposing apparatus according to claim 1 is characterized by a solder ball disposing apparatus for making a solder ball stationary in a state where the ball is in contact with a first bonding surface of a pad formed on a slider held by slider holding means for a disk drive; and a second bonding surface of a pad formed on an end portion of a lead disposed on the slider holding means, and positioned in the vicinity of and substantially perpendicularly to the plane including the first bonding surface, and the solder ball disposing apparatus includes:
a solder-ball feeder unit positioned apart from the slider holding means that holds the slider in which each of the first and second bonding surfaces is held obliquely from a vertical direction by a prescribed distance, accommodates a plurality of solder balls in the internal space thereof, and has ejecting holes formed on the bottom of the internal space for ejecting a gas to blow the solder balls and solder-ball discharging holes formed in the upper portion of the internal space for discharging the blown solder balls out of the solder-ball feeder unit; and
a suction pad having a suction hole formed on the tip for sucking solder balls discharged from the discharging holes into the suction hole, and transporting and releasing the solder balls to and at the location where the solder balls contact the first and/or second bonding surface(s), or approach the first and second bonding surfaces.